a) Define pulsus paradoxus and describe the mechanism by which this occurs in acute pericardial tamponade. (20% marks)
b) List four methods by which pulsus paradoxus may be elicited clinically. (20% marks)
c) List four other clinical signs of acute pericardial tamponade. (20% marks)
d) List four electrocardiographic findings suggestive of pericarditis with cardiac tamponade. (20% marks)
e) List four echocardiographic features of cardiac tamponade. (20% marks)
Pulsus paradoxus is an exaggeration (> 12 mmHg or 10%) of the normal inspiratory decrease in systemic blood pressure.
Decreased intrathoracic pressure with inspiration results in increased venous return to right heart and bulge of IVS to left. Because the ventricle can normally also expand outward, this septal shift is usually small, and the difference in the blood pressure is therefore small between inspiration and expiration (<10 mmHg). With tamponade, the left ventricle cannot expand outward, so the septal shift is exaggerated and the difference in BP is larger. Also, the relatively higher negative pressure in the pulmonary circulation compared to the left atrium in patients with pericardial pathology pooling of blood in pulmonary veins during inspiration resulting in decreased LV stroke volume.
Palpation of pulse- disappears in deep inspiration
Sphygmomanometer- Korotkoffs sounds first heard in expiration only and then in inspiration with progressive deflation
Pulse Oximeter-particularly useful in paediatrics
Arterial pressure trace- exaggerated fall of systolic pressure in inspiration
Elevated JVP (neck vein distension with inspiration- Kussmaul’s sign) Muffled heart sounds
Exaggerated drop in diastolic CVP (Friedrich’s sign)
Absent y descent on CVP trace
Clinical signs of shock- decreased peripheral perfusion, slow capillary refill, oliguria, confusion.
Low QRS voltage trace Electrical alternans
Global concave ST elevation PR depression
Visible pericardial effusion
Diastolic collapse of Right Atrium and Right Ventricle
Respiratory variation in left and right sided volumes. Atrial and ventricular septa move leftward during inspiration and rightward during expiration
Mitral and Tricuspid flow velocities are increased and out of phase. Mitral flow is increased on the first beat of inspiration and tricuspid flow is increased on expiration.
The IVC is distended and does not collapse on inspiration
a) The definition of pulsus paradoxus used by the college is from Curtiss et al (1988) who demonstrated that 12 mmHg and 9% systolic variation (not 10%) are the 95% confidence limits for diagnosis of moderate or severe tamponade. Most textbooks instead use 10mmHg as a convenient round number, described by Swami and Spodick (2003) as "a quasi arbitrary but practical level".
b) there are in fact only four methods known:
c) These are the clinical signs of cardiac tamponade (some available mainly via invasive monitoring waveforms)
d) Electrocardiograhic features of pericarditis with tamponade are:
e) Echocardiographic features listed here are from Pérez-Casares et al (2017)
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